A new report by some of the nation’s top environmental groups on Tuesday shows that approval of the Keystone XL tar sands pipeline would add at least 181 million metric tons of carbon dioxide to the atmosphere, the equivalent of pollution from 37.7 million cars or 51 newly built coal-fired power plants.

The report was researched and authored by Oil Change International with input and review by the Natural Resources Defense Council, 350.org, Environment America, National Wildlife Federation, Friends of the Earth, the Sierra Club and Greenpeace. …

The key findings of the group’s research concluded that:

The 181 million metric tons of (CO2e) from Keystone XL is equivalent to the tailpipe emissions from more than 37.7 million cars. This is more cars than are currently registered on the entire West Coast (California, Washington, and Oregon), plus Florida, Michigan, and New York – combined.

Between 2015 and 2050, the pipeline alone would result in emissions of 6.34 billion metric tons of CO2e. This amount is greater than the 2011 total annual carbon dioxide emissions of the United States.

The International Energy Agency has said that two-thirds of known fossil fuel reserves must remain undeveloped if we are to avoid a 2 degree C temperature rise. Constructing the Keystone XL pipeline and developing the tar sands make that goal far more difficult, if not impossible, to reach.

Despite all this, said 350.org executive director May Boeve, “the State Department says that the pipeline would have negligible climate impacts.”

Boeve’s group is among those urging its members this week to use the public comment period set out by the State Department to voice their opposition to the tar sands pipeline and hopes that this new report will help inform the broader public about the inherent dangers of Keystone XL, whether it eventually spills or not.